Skip the 30-minute nap: how long to sleep in the afternoon

Amber Brooks and Leon Lack gave 24 adults five afternoons in a laboratory: no nap, then naps of 5, 10, 20 and 30 minutes of measured sleep, each at 3 p.m. after a night cut to about 5 hours in bed. The 10-minute nap improved every measure they took, and some of those gains held for 155 minutes. The 30-minute nap left people worse off for a stretch before anything improved ¹. I train teams in other countries and run about 5,000 km a year, so an afternoon goes either to a room of people or to a second run, and I had been picking nap lengths from whatever the schedule left over.

What each length buys.

In that design, the 5-minute nap did close to nothing against the no-nap control. The 10-minute nap lifted sleep latency, subjective sleepiness, fatigue, vigour and cognitive performance from the first test onward. The 20-minute nap produced the same kind of gains, except they appeared 35 minutes after waking and ran out at 125. The 30-minute nap opened with a period of impaired alertness and performance, then delivered improvements that lasted to 155 minutes ¹.

That opening period is sleep inertia, and it has been measured against sleep loss itself. Wertz and colleagues kept 9 people in a laboratory for six days and compared two states on a 2-minute serial addition test: the first 20 minutes after waking from 8 hours of sleep, and 26 hours of monitored wakefulness. Scores right after waking came out below the sleep-deprived ones ². Hilditch and McHill reviewed the literature on this sleep inertia and put typical recovery back to pre-sleep performance inside 30 minutes, with full recovery closer to an hour. Waking out of slow-wave sleep after a nap of 60 minutes or less did not make the inertia worse ³.

Pooled across the cognitive literature, the average gain is small. Dutheil and colleagues took 11 studies and 381 participants and found an overall effect of 0.18 on cognitive performance (95% CI 0.09 to 0.27) and 0.29 on alertness ⁴. Their mean nap ran 55 minutes, so that average mixes the short naps with the long ones and the groggy wake-ups with the clean ones.

45 minutes before the legs work.

Omar Boukhris ran 17 physically active men through four conditions before a 5-metre shuttle run: no nap, and nap opportunities of 25, 35 and 45 minutes. Best distance rose 6% after the 25-minute opportunity and 9% after the 45. Total distance gained 8% after the 45-minute nap against 3% after the two shorter ones, and rated exertion came out around 20% lower after the long nap than after the short one or no nap at all ⁵.

Boukhris and colleagues later pooled 18 studies of naps taken after a normal night of 7 to 9 hours. In the same shuttle run, effect sizes reached 1.026 for highest distance, 0.737 for total distance and 0.839 for the fatigue index. Muscle force did not move (0.175, p = 0.267) ⁶. Past 60 minutes the nap picks up REM sleep. Sara Mednick's team found that naps of 60 to 90 minutes containing both slow-wave and REM sleep produced as much learning on a visual texture task as a full 8 hours did ⁷.

Caffeine taken before the nap beat either one alone. Reyner and Horne sat 12 sleepy volunteers in a car simulator for a 2-hour monotonous afternoon drive, with treatments taken during a 30-minute break beforehand. Caffeine of 200 mg on its own brought driving incidents down to 34% of the placebo level. Caffeine followed by a nap of under 15 minutes brought them to 9%. Breaks where people dozed without reaching sleep still helped ⁸.

The usual objection to an afternoon nap is the night that follows it. Boukhris's group measured that night with EEG on 14 student athletes: a 25-minute opportunity starting at 14:35, a 90-minute one starting at 13:30, both ending at 15:00, against no nap. Total sleep time came out at 7 h 13 min after no nap, 7 h 05 after the short nap and 7 h 01 after the long one, with bedtime, wake time, time awake after sleep onset and the light, deep and REM stages unchanged ⁹.

The athlete numbers rest on one test.

Most of the physical evidence runs through a single protocol, that 5-metre shuttle run, on crossover samples of 14 to 24 people from a handful of laboratories. Those studies hand out a nap opportunity rather than a measured dose of sleep, so part of the gain belongs to lying down in a dark room. Muscle force stayed flat in the pooled analysis ⁶, which rules the nap out as preparation for lifting. Milner and Cote list the moderators to expect when you test this on yourself: nap length, time of day and how much napping experience someone has all move the result, with naps under 30 minutes carrying the clearest benefit ¹⁰.

The protocol.

1. Pick the length from the task, and skip 30 minutes. 10 minutes of sleep when you work right after the alarm. 20 minutes when you have 35 minutes of slack before the work starts. 45 minutes before a run, a hard session or an afternoon on your feet in front of a room, stretching to 90 after a bad night.
2. Budget falling asleep into the alarm. A 25-minute alarm yields roughly 10 to 15 minutes of sleep for most people. Time your own latency on two naps with a watch, then move the alarm to hit the target.
3. End the nap by 15:00. Both durations in the EEG trial finished at that hour and left the following night intact ⁹.
4. Guard the 10 minutes after the alarm. No decisions, no hard effort, no driving. The minutes right after waking are the worst of your day for arithmetic ². After a nap longer than 30 minutes, give it 20 minutes, with light and movement.
5. Caffeine before the pillow, never after. 200 mg, then lie down for under 15 minutes, for an evening drive or a late session ⁸.
6. Stay down when sleep does not come. The drivers who dozed without sleeping kept most of the benefit ⁸.
7. Run 3 attempts before you judge it. Napping experience changes what a nap does for you ¹⁰.
8. Log one number. Rated exertion for the session, or errors caught in review, on napped and non-napped days for two weeks. Compare the two lists at the end of the fortnight instead of trusting how any single nap felt.

Sources.

1. Brooks, A., & Lack, L. (2006). A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep, 29(6), 831-840. doi:10.1093/sleep/29.6.831
2. Wertz, A. T., Ronda, J. M., Czeisler, C. A., & Wright, K. P. (2006). Effects of sleep inertia on cognition. JAMA, 295(2). doi:10.1001/jama.295.2.163
3. Hilditch, C. J., & McHill, A. W. (2019). Sleep inertia: current insights. Nature and Science of Sleep, 11, 155-165. doi:10.2147/NSS.S188911
4. Dutheil, F., Danini, B., Bagheri, R., et al. (2021). Effects of a short daytime nap on the cognitive performance: a systematic review and meta-analysis. International Journal of Environmental Research and Public Health, 18(19), 10212. doi:10.3390/ijerph181910212
5. Boukhris, O., Abdessalem, R., Ammar, A., et al. (2019). Nap opportunity during the daytime affects performance and perceived exertion in 5-m shuttle run test. Frontiers in Physiology, 10, 779. doi:10.3389/fphys.2019.00779
6. Boukhris, O., Trabelsi, K., Suppiah, H., et al. (2023). The impact of daytime napping following normal night-time sleep on physical performance: a systematic review, meta-analysis and meta-regression. Sports Medicine. doi:10.1007/s40279-023-01920-2
7. Mednick, S., Nakayama, K., & Stickgold, R. (2003). Sleep-dependent learning: a nap is as good as a night. Nature Neuroscience, 6(7), 697-698. doi:10.1038/nn1078
8. Reyner, L. A., & Horne, J. A. (1997). Suppression of sleepiness in drivers: combination of caffeine with a short nap. Psychophysiology, 34(6), 721-725. doi:10.1111/j.1469-8986.1997.tb02148.x
9. Boukhris, O., Suppiah, H., & Driller, M. (2026). The influence of 25- and 90-min afternoon nap opportunities on subsequent nighttime sleep in student athletes. Journal of Sleep Research, 35(1), e70120. doi:10.1111/jsr.70120
10. Milner, C. E., & Cote, K. A. (2009). Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping. Journal of Sleep Research, 18(2), 272-281. doi:10.1111/j.1365-2869.2008.00718.x